FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] The multi-pass membrane protein encoded by this gene belongs to the G-protein coupled receptor 3 family and GABA-B receptor subfamily. The GABA-B receptors inhibit neuronal activity through G protein-coupled second-messenger systems, which regulate the release of neurotransmitters, and the activity of ion channels and adenylyl cyclase. This receptor subunit forms an active heterodimeric complex with GABA-B receptor subunit 1, neither of which is effective on its own. Allelic variants of this gene have been associated with nicotine dependence.[provided by RefSeq, Jan 2010] PHENOTYPE: Homozygous mutation of this gene results in clonic seizures, hyperactivity, hyperalgesia in response to thermal or mechanical stimuli, increased anxiety, and decreased depression-related behavior. [provided by MGI curators]